Eliana Rocchini

Some recent developments in the characterization of ceria-based catalysts

Abstract In the present paper some recent developments in the use of ceria and related materials in catalysis are considered. The relevant features of ceria–zirconia and ceria–silica as oxygen storage components are briefly reviewed with a special focus on the characterization and relationship between oxygen uptake/release and structural properties.

Ruthenium(II) complexes with chelated RCE2 − ions (E=O or S) bearing 1-(diphenylphosphino)-2-(2-pyridyl)ethane (ppye). Crystal structures of cis,trans-[Ru(RCO2)(ppye)2]PF6 (R=H or CH3)

Abstract The Ru(II) carboxylates c , t -[Ru(RCO 2 )(ppye) 2 ]PF 6 [ppye=1-(diphenylphosphino)-2-(2-pyridyl)ethane; R=H, CH 3 , CF 3 , cyclo -C 6 H 11 , and C 6 H 5 ] have been prepared from c , t , c -[Ru(CH 3 CN) 2 (ppye) 2 ](PF 6 ) 2 by reaction with RCO 2 Na salts. The complexes have been characterised in solution by multinuclear NMR, and the structure in the solid state for both acetate and formate has been determined by X-ray diffraction analysis. Complex c , t -[Ru(HCO 2 )(ppye) 2 ]PF 6 undergoes substitution of CO 2 with CS 2 affording c , t -[Ru(HCS 2 )(ppye) 2 ]PF 6 , which is converted into the stable t , c via the c , c isomer. Complexes c , t -[Ru(RCS 2 )(ppye) 2 ]PF 6 [R=CH 3 CH 2 O or (CH 3 ) 2 N] have also been prepared and characterised. Both species slowly isomerise into the stable c , c derivatives. A variable-temperature 1 H NMR investigation has evidenced a fluxional behaviour in solution of all complexes of the type c , t -[Ru(RCE 2 )(ppye) 2 ]PF 6 (E=O or S), which is ascribable to a restricted rotation of phenyl rings of ppye. The protonation reaction of c , t -[Ru(CH 3 CO 2 )(ppye) 2 ] + has also been studied. Dicationic c , t -[RuL 2 (ppye) 2 ] 2+ complexes are formed when HBF 4 is used in the presence of a coordinating solvent L [L=CH 3 CN or (CH 3 ) 2 SO]. Conversely, carboxylic acids stronger than CH 3 CO 2 H react with c , t -[Ru(CH 3 CO 2 )(ppye) 2 ] + affording c , t -[Ru(RCO 2 )(ppye) 2 ] + complexes.

Turning dihydrogen gas into a strong acid. Formation and reactions of the very acidic ruthenium dihydrogen complexes trans-[Ru(H2)(CNH){PPh2(CH2)nPPh2}2][O3SCF3]2 (n = 2 or 3)

New, very acidic ruthenium dihydrogen complexes containing the hydrogen isocyanide ligand have been synthesised; when formed under 1 atm H2 they have been shown to spontaneously eliminate trifluoromethylsulfonic acid.